Audible alert systems are used in various types of motor vehicles to alert pedestrians, bicyclists, etc. that a vehicle is backing up. This is important because the driver of the vehicle may not be able to see a person behind the vehicle if the person is in a so-called “blind-spot.” As such, these types of systems have become commonplace in large delivery trucks, heavy machinery, etc. where it may be particularly hard to see a person behind the vehicle.
Such systems are also becoming more popular in passenger vehicles such as cars and small trucks. For example, U.S. Pat. No. 4,851,813 to Gottlieb discloses a combination back-up light and sound emitting device for an automotive vehicle including a housing having a base at one end and a socket at the other end. A light bulb is mounted in the socket of the housing and a sound emitting device is also mounted in the housing. The base may be inserted in a vehicle back-up bulb socket so that the sound emitting device and the light bulb are activated when the vehicle is in reverse.
While such prior art systems are particularly useful for alerting people outside the vehicle that the vehicle is backing up toward them, these systems indiscriminately emit sound whenever the vehicle is placed in reverse. Because the emitted sound is intended to serve as a warning indicator, it is generally quite loud and often shrill. As a result, it may become bothersome to a driver to have this alert tone emitted whenever the vehicle is placed in reverse. This may be especially true when there are no objects or people adjacent the rear of the vehicle. Furthermore, such prior art systems do nothing to alert the driver whether an object or person is actually behind the vehicle. Thus, even if a person is alerted to a vehicle backing up toward him, he may not be able to get out of the way in time.
Several driver alerting devices have been created to address this problem. For example, some back-up warning systems include a transceiver mounted on a rear end of a vehicle for detecting objects close to the vehicle while the vehicle is in reverse. For example, U.S. Pat. No. RE 34,773; U.S. Pat. Nos. 4,797,673; 4,864,298; and 5,028,920 to Dombrowski disclose a driver alerting device including a transceiver mounted on the rear end of a vehicle (e.g., on the bumper) that directs a wave output rearwardly from the vehicle. Return wave signals from objects within range of the transceiver are picked up by an antenna and supplied to the transceiver. Any resulting Doppler shift detected by the transceiver causes the transceiver to provide an audible alert within the passenger compartment. The device may be electrically connected to the reverse gear of the vehicle for activation when the vehicle transmission is engaged in the reverse gear. One limitation of such devices is that they may be relatively bulky and require mounting on the back of the vehicle in a conspicuous location, such as on the vehicle's bumper. Accordingly, these devices may be unsightly and they may also require screws, etc. to securely fasten the device to the vehicle. Thus, there may be a significant potential for damage to the vehicle during installation, and this process may take a substantial amount of time to complete. Further, such devices protrude from the bumper and may therefore be damaged or even knocked off the vehicle. Additionally, not all vehicles have a suitable mounting location for such devices.